(BOSTON) — The trial began on Tuesday in the case of a young Massachusetts woman who is accused of encouraging her 18-year-old boyfriend to kill himself.

Michelle Carter, 20, is charged with involuntary manslaughter after she allegedly urged her then boyfriend Conrad Roy to commit suicide in 2014, purportedly documented in thousands of text messages.

“She used Conrad as a pawn in a sick game of life and death for attention,” prosecutor Maryclare Flynn said in court on Tuesday.

Prosecutors revealed that Carter, then 17, exchanged 20,000 text messages with Roy, and more than 1,000 of those were sent in the days leading up to his death.

Among them included a text from Carter saying Roy was “overthinking” the plan.

“You’re hesitant because you keeping over thinking it and keep pushing it off. You just need to do it, Conrad,” the message read.

Roy died of carbon monoxide poisoning after locking himself in his truck. According to prosecutors, Carter urged him to go to the parking lot and replied, “You are ready and prepared, all you have to do is turn on the generator and you will be free and happy.”

Prosecutors added that Carter displayed frustration and anger when Roy delayed the plan, and that she “ordered him back and then listened as he cried, took his last breath.”

Conrad Roy’s mother, Lynn Roy, took the stand and became visibly upset and tearful as she explained the state of her son’s mental health.

“I knew he was a little depressed but I thought it, he was doing great. I mean he just graduated from high school, got his captain’s license and I thought everything was moving forward, not backward,” she said.

Conrad Roy’s then-13-year-old sister testified that she received a text on the day of his death from Carter that read, “Find him yet?” She also said that just two days before his funeral, Carter asked for some of his ashes.

“She … assured him that his family would understand why he did it. She researched logistics and reassured him that he was likely to succeed,” said Flynn.

If convicted, Carter could face 20 years in prison. The defense argues it was Conrad Roy who in his own words dragged her into his suicide plans.

“It is not a homicide,” lawyers for Carter said. “The evidence of the texting is overwhelming that Conrad Roy was on this path to take his own life for years,” the defense added.

Carter waived her jury trial, leaving her fate in the hands of the judge.